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Falklands Conservation |
Update on Cobb's Wren
by Robin Woods
Cobb's Wren Troglodytes cobbi is endemic to the Falkland Islands. In 1994, BirdLife International classed Cobb's Wren as 'Vulnerable' because of the small scattered population restricted to geographically isolated areas of the Falklands and the destruction of its favoured tussac grass habitat over many years.
Status 1983/4 - 1992/3
During the ten year survey of breeding birds which led to the publication of our Atlas of Breeding Birds of the Falkland Islands (1997)*, the population was calculated to be only about 2,000 pairs. Cobb's Wren was found in 25 of the10km grid squares and breeding was reported as probable or confirmed in 17 squares. All records came from offshore islands. A closer look at the data revealed that Cobb's Wren was only recorded on 12 islands in groups separated from each other by about 40km of ocean.
Further Survey Work 1997/8
During the Johnny Rook Survey a total of 57 islands were visited. Records were kept of the bird species present and whether there was evidence of rats or mice. On the 23 islands where the presence of rats was confirmed, we could not find Cobb's Wren. In contrast, the Grass Wren was found on 21 islands with rats. This smaller and apparently weaker wren can survive with rats, probably because it feeds mostly above ground level in thick vegetation and not on beaches among boulders.
Population Estimate Now Trebled
Taking into account all records from the Atlas and the later visits, Cobb's Wren has now been recorded in 37 grid squares, with breeding probable or confirmed in 33 squares. New population calculations suggest that there are about 6,000 pairs on 29 islands or islets, which is a better situation for the species than was previously thought. However, populations are still isolated in island groups and it is fairly clear that if rats spread to any of the predator-free islands, then the Cobb's Wren population would be destroyed.
Rats keep Songbirds off New Nature Reserve
Two small islands in Queen Charlotte Bay off Spring Point, West Falkland were bought in 1998 by Falklands Conservation, through the generosity of members. It was obvious that rats were present when Mike Morrison and I visited in October 1998. There was no evidence of Cobb's Wren nor indeed Tussacbird, Black-throated Finch, Long-tailed Meadowlark and we detected only two singing Grass Wrens on Double Island and one on Outer Island. We found only 24 bird species on these islands, which both have good cover of mature tussac grass. A solitary Falkland Thrush sang on Outer Island, and it seemed likely that there was a pair of Dark-faced Ground-tyrants on each island. This lack of songbirds is absolutely typical of small islands infested with rats. Getting rid of the rats here has been seen as an important objective since the Islands' acquisition.
Plans Afoot to Eradicate Rats
Recently, biologists from New Zealand visiting the Falklands heard about our rat problems. A scheme to eradicate them from Outer and Double Islands (along with two further islands off East Falkland) has been drawn up. It is an intriguing thought that ridding these small tussac islands of rats could allow recolonisation by songbirds, particularly Cobb's Wren and the Tussacbird. Let us hope that funding is found for this exercise (to take place in 2000/01) which would be the first of its kind on a Nature Reserve in the Falklands.
Surveying Falkland Islands Flora
by David Broughton and Jim McAdam
An 18 month Darwin Initiative project on the Falkland Islands flora run by Queens University of Belfast began in October 1999. The Darwin Initiative is a UK Government fund set up after the 1992 Earth Summit to enable British biologists to assist partner countries to conserve their biological diversity and implement the Biodiversity Convention. Projects funded under the Initiative always involve a partnership with an organisation in the host country - in this case the partner is Falklands Conservation.
Considering that it is such a fundamental resource the flora of the Falkland Islands has been poorly studied. This Project will be the first thorough and systematic study of the distribution and status of the flora. The Project is also important as its is unbiased ie no species is deemed more important than another. In the past has there has often been a bias towards the more rare and unusual plants whilst the common and more ecological important species have been vastly under-recorded.
The end results will be not only a representative atlas of the Falklands flora but also a computer database held by Falklands Conservation, containing all the data from the plant surveys. This will be a significant, and hopefully growing, resource for the future. It is hoped that the data will remain freely available in the Falkland Islands for conservation planning (including monitoring the spread of non-native species) for tourism, agriculture, scientific research, education, and for helping to develop novel, sustainable uses for Falklands flora.
After three months fieldwork we already have a much better understanding of the status and distribution of the Falkland Islands flora. For example:
The Darwin programme is incorporating all records submitted for Falklands Conservation's native plant survey, and species records are welcome from anyone throughout the course of the Project, so please get involved! In fact the more contributors we have the better as this will help to ensure that the data truly reflects the distribution of the flora. Even well surveyed areas continue to throw up new surprises. Plant records (including the date of sighting, a precise location, and if possible a grid reference) can be sent to David Broughton, c/o Falklands Conservation, PO Box 26, Stanley, Falkland Islands or to David/Jim McAdam at the Dept of Applied Plant Science, Queens University of Belfast, Newforge Lane, Belfast BT9 5PX, Northern Ireland.
Seabird Monitoring Programme Results from 15th Year, 1999-2000
by Andrea Clausen, Field Science Officer
Sites surveyed
Following a review carried out by Dr Klemens Putz, which analysed all data collected over the past 13 years of the Programme, in additional to historical sites, counts were made at Sea Lion Island (to the south east) and Saunders Island (in the north west) for the 1999-2000 season. Diet sampling was carried out at Volunteers Point and Seal Bay (to the north east) and at Sea Lion and Saunders Islands.
Gentoo Penguins
Productivity ranged from 0.59 to 1.45 chicks per breeding pair. These figures are generally higher than in the previous season (0.35 to 1.10 chicks per breeding pair). Despite our unusually warm dry summer there was no evidence between November - January of any negative effect on the breeding birds. However, anecdotal evidence suggests higher than normal mortality rates due to hot weather after this. Breeding pair numbers were up in 6 out of 7 of the historical sites, with one colony experiencing a 77% increase.
Diet samples are currently being worked up in the Department of Fisheries. However, to date there appears to be a considerable amount of squid. Four species have been identified Loligo gahi, Moroteuthis ingens, Gonatus antarcticus and Illex argentinus, with the commercial species Loligo gahi found most frequently. Gentoo penguins also took considerable amounts of Krill (Munida gregaria) and fish (mainly a non-commercial species from the herring family and Patagonotothenids).
Rockhopper Penguins
Rockhoppers appear to have had an average year. Productivity ranged from 0.65 to 0.91 chicks per breeding pair. A pilot study to investigate whether or not breeding pairs could successfully rear 2 chicks to fledging was carried out at Seal Bay. A sub-colony of 103 breeding pairs was monitored over a 6 week period and several attempts made to mark chicks/nests. Unfortunately our methods were not successful, and although we had some nests with 2 chicks right up to the time of creching, after this nests were lost and chicks could not be identified. We will continue to investigate this theory.
The main diet component was fish, predominantly unidentifiable 'whitebait' (juvenile fish), although smaller quantities of squid, krill and amphipods Thermisto gaudichaudi were found.
Magellanic Penguins
At Gypsy Cove all occupied burrows and resulting chicks, were counted. Productivity was lower (0.82 chicks per breeding pair) than the previous season (1.49 chicks per breeding pair) although the number of occupied burrows was up (332 compared to 174 in 1998/99), indicating a rise in the number of non-breeders or failed breeders. At other sites densities of occupied burrows were assessed as well as the productivity in randomly selected areas. Productivity ranged from 0.63 to 0.75 chicks per breeding pair. These values are within those found for Magellanic penguins at the historically monitored sites. The diet of Magellanic penguins included all species found in Gentoo and Rockhopper penguins.
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Patron: HRH The Duke of York CVO ADC Member of the International Union for Conservation of Nature | BirdLife International Representative |